Truck idle surges and dies out.
02-09-2017, 11:11 PM
#1
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Truck idle surges and dies out.
05 F150 5.4L 3v
I just changed COPs and plugs, cleaned the MAF and throttle body, changed fuel and air filter, and check valve. When I fire up the truck the engine, the engine runs up to about 1500rpm and then goes to a normal idle and after about a minute the idle starts to fluctuate from normal to about 450-500rpm a couple of times and then the engine dies out. Who has a clue as to what's going on? Also, Crank Position Sensor has been changed. This is frustrating.
I just changed COPs and plugs, cleaned the MAF and throttle body, changed fuel and air filter, and check valve. When I fire up the truck the engine, the engine runs up to about 1500rpm and then goes to a normal idle and after about a minute the idle starts to fluctuate from normal to about 450-500rpm a couple of times and then the engine dies out. Who has a clue as to what's going on? Also, Crank Position Sensor has been changed. This is frustrating.
02-10-2017, 06:37 AM
#2
Mark
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Did you remove the throttle body to clean it or did you clean it while attached to the manifold ?
02-11-2017, 07:48 PM
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02-12-2017, 04:25 AM
#7
05 5.4l 3v s.crew lariat
Seems like you have done a lot to this truck
I don't use non oem coils . I have seven orig coils at 170k .
This motor requires everything to be perfect to run right .
Lets start by looking at plug changes . Do you have the correct plugs for the heads that are on the engine . You mention updated heads .
The plug holes must be cleaned before removing plugs. . New plugs require new boots and springs . Spark Plug extended hole should be cleaned out with carb cleaner,that carbon can break new plugs and change heat range of plug . A coat hanger with cloth strips seems to be favored. Many have found that cures a lot of their problems.Forget seafoam stuff .
Are you using dielectric grease on new boots . I always change boots . The boots are subject to 50,000 volts or so . any moisture or dirt is not going to be good . Use a small amount on each end to keep moisture out , This also stops heat seizing . Boots are damaged by oil ,heat,anti freeze,anti seize .Keep your hands clean anti seize will cause tracking there is metal in it .
If you cleaned the carbon out of the holes you don't need to use nickel anti seize on tips . If you do use it ,only a thin coat nowhere near the tips .
Plugs should always be started by finger feel and torqued down to 25-28 pounds . Loose plugs are common on this engine . If you get blow by you are going to see damage on boots and ceramic as well as carbon on the threads .
Change plugs before 50k ,its not worth it to go farther . Keep plug area free of antifreeze ,oil etc . Don't wash this engine .
Now for the throttle body , I lost mine around 60k . There was a problem with the original series. Their are numbers on throttle body for defective series started with 3L new improved I believe was 8L . I bought a new one off ebay for around $200.
Next you are at 125k or more and you may be looking at a timing job -depending .
This motor requires everything to be perfect to run right .
Lets start by looking at plug changes . Do you have the correct plugs for the heads that are on the engine . You mention updated heads .
The plug holes must be cleaned before removing plugs. . New plugs require new boots and springs . Spark Plug extended hole should be cleaned out with carb cleaner,that carbon can break new plugs and change heat range of plug . A coat hanger with cloth strips seems to be favored. Many have found that cures a lot of their problems.Forget seafoam stuff .
Are you using dielectric grease on new boots . I always change boots . The boots are subject to 50,000 volts or so . any moisture or dirt is not going to be good . Use a small amount on each end to keep moisture out , This also stops heat seizing . Boots are damaged by oil ,heat,anti freeze,anti seize .Keep your hands clean anti seize will cause tracking there is metal in it .
If you cleaned the carbon out of the holes you don't need to use nickel anti seize on tips . If you do use it ,only a thin coat nowhere near the tips .
Plugs should always be started by finger feel and torqued down to 25-28 pounds . Loose plugs are common on this engine . If you get blow by you are going to see damage on boots and ceramic as well as carbon on the threads .
Change plugs before 50k ,its not worth it to go farther . Keep plug area free of antifreeze ,oil etc . Don't wash this engine .
Now for the throttle body , I lost mine around 60k . There was a problem with the original series. Their are numbers on throttle body for defective series started with 3L new improved I believe was 8L . I bought a new one off ebay for around $200.
Next you are at 125k or more and you may be looking at a timing job -depending .
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02-12-2017, 10:41 AM
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I used Motorcraft plugs, I've read plenty that this is the only way to go. I also updated the Throttle Body to the C model, which is the latest for the 11th Gen. I may of pinched the gasket installing so I'll be removing it today and checking. I use dielectric grease on every electrical connection in a automobile unless it's not called for.
I also blew out every plug hole and then cleaned and vacuumed it, I use a shop vac with connections to clean tight spaces and computer equipment. You be surprised how well it works and yes, the plugs were in place when I did this. I used a modified brass brush from my rifle cleaning kit to scrape everything out. I did use Denso COPs but went back to Motorcraft, better results and no headaches. I did use nickel anti-seize but only on the barrels of the plugs and was a very thin coat. The torque is about 25ft/lbs.
No codes were thrown but today I am disconnecting to the MAF and starting the process of elimination all over.
I also blew out every plug hole and then cleaned and vacuumed it, I use a shop vac with connections to clean tight spaces and computer equipment. You be surprised how well it works and yes, the plugs were in place when I did this. I used a modified brass brush from my rifle cleaning kit to scrape everything out. I did use Denso COPs but went back to Motorcraft, better results and no headaches. I did use nickel anti-seize but only on the barrels of the plugs and was a very thin coat. The torque is about 25ft/lbs.
No codes were thrown but today I am disconnecting to the MAF and starting the process of elimination all over.
02-12-2017, 12:14 PM
#10
05 5.4l 3v s.crew lariat
Sounds like you are on top of it
Let us know when you find the problem 
A vacuum leak can cause these problems , Homemade smoke machines are on you tube . The intake runner control is bad about that . Its behind and under intake manifold. Hard to deal with .
Intake manifold gasket is another and there's a check for that .
Vacuum circuit includes gas tank , gas cap and purge solenoid .
Rats chew on hoses and wires .
A vacuum leak can cause these problems , Homemade smoke machines are on you tube . The intake runner control is bad about that . Its behind and under intake manifold. Hard to deal with .
Intake manifold gasket is another and there's a check for that .
Vacuum circuit includes gas tank , gas cap and purge solenoid .
Rats chew on hoses and wires .